蒙古国东北部脑明特铜矿床成矿岩体年龄、Hf同位素、地球化学特征及其对成矿构造背景的约束  

Geochronology,Hf isotope,geochemical characteristics of the metallogenic rock mass in Nomint copper deposit,Northeastern Mongolia,and its constraint on metallogenic tectonic setting

作　　者：吴涛涛[1,2,3] 陈聪 王庆双 姚远 周永恒[1,2] 柴璐[1,2] 鲍庆中[1,2] WU Taotao;CHEN Cong;WANG Qingshuang;YAO Yuan;ZHOU Yongheng;CHAI Lu;BAO Qingzhong(Shenyang Center,China Geological Survey,Shenyang 110034,Liaoning,China;Northeast Science&Technology Innovation Center,China Geological Survey,Shenyang 110034,Liaoning,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]中国地质调查局东北地质科技创新中心,辽宁沈阳110034 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质通报》2024年第5期726-742,共17页Geological Bulletin of China

基　　金：中国地质调查局项目《东北亚和欧洲国际合作地质调查》(编号:DD20230130);《中蒙俄毗邻区大型铀、铜资源基地评价》(编号:DD20190438)。

摘　　要：脑明特中型铜矿床位于蒙古-鄂霍茨克缝合带中部,是蒙古国东北部已知规模最大的铜矿床。为探究岩体与成矿的关系,在矿床学研究的基础上,对该矿床成矿岩体开展了锆石U-Pb年代学、微量元素及Hf同位素地球化学研究。结果显示:成矿岩体的锆石U-Pb年龄为166.3±2.3 Ma和162.6±1.6 Ma,表明该成矿岩体应为中侏罗世晚期岩浆作用的产物;岩石化学组成上,成矿岩体主量元素SiO_(2)(62.81%~66.03%)>56%,Al_(2)O_(3)(15.01%~15.77%)>15%,MgO(2.06%~2.72%)<3%,K_(2)O/Na_(2)O<1,微量元素具有轻稀土元素相对富集,重稀土元素相对亏损,Eu异常不明显和贫Y(含量为10.67×10^(-6)~14.05×10^(-6),<18×10^(-6))、Yb(含量为1.20×10^(-6)~1.65×10^(-6),<1.9×10^(-6)),富集Sr(含量为547.6×10^(-6)~661.8×10^(-6),>400×10^(-6))的特点,表明成矿岩体具有埃达克质岩石的地球化学特征。同时,成矿岩体具有相对较高的Mg^(#)和Cr、Ni含量,与源自拆沉下地壳熔融形成的埃达克岩相似。在Hf同位素组成上,该岩体具有较低的ε_(Hf)(t)正值(0.3~4.3)和中—新元古代模式年龄(T_(DM2)=1183~937 Ma),推测岩浆上升过程中混染了部分中—新元古代基底岩石组分。综合研究表明,脑明特铜矿床成矿岩体岩浆起源于拆沉下地壳的部分熔融,形成于中侏罗世晚期蒙古-鄂霍茨克洋闭合后的陆内伸展环境。The Nomint medium-scale copper deposit,located in the central part of the Mongolia-Okhotsk suture zone,is the largest known copper deposit in the northeastern part of Mongolia.To explore the relationship between the rock mass and mineralization,this paper conducts zircon U-Pb chronology,trace element,and Hf isotopic geochemical research on the ore-forming rock mass of this deposit,based on mineralogical studies.The results show that the biotite granodiorite yielded zircon U-Pb ages of 166.3±2.3 Ma and 162.6±1.6 Ma,respectively,representing the products of the late Middle Jurassic magmatism;In the geochemical composition,the metallogenic rock mass are SiO_(2)(62.81%~66.03%)>56%,Al_(2)O_(3)(15.01%~15.77%)>15%,MgO(2.06%~2.72%)<3%,K_(2)O/Na_(2)O<1,trace elements are relatively enriched in LREE and relatively deficient in HREE.Eu anomaly was not obvious and Y(10.67×10^(-6)~14.05×10^(-6),<18×10^(-6))and Yb(1.20×10^(-6)~1.65×10^(-6),<1.9×10^(-6))were poor,and Sr enrichment(547.6×10^(-6)~661.8×10^(-6),greater than 400×10^(-6)).It indicates that the metallogenic rock mass has the geochemical characteristics of Adakite rock.In the meanwhile,the metallogenic rock mass has relatively high Mg^(#),Cr and Ni contents,which is similar to Adakite formed from melting of crust under subsidence.In terms of Hf isotopic composition,the pluton has a lowε_(Hf)(t)value(0.3~4.3)and a Mesoproterozoic model age(T_(DM2)=1183~937 Ma),suggesting that some Mesoproterozoic basement rock components were mixed during the magmatic rise.The comprehensive research indicates that the metallogenic rock magma of the deposit originated from partial melting of the lower crustal delamination,formed in an intracontinental extensional environment following the closure of the Mongolia-Okhotsk Ocean in the late Middle Jurassic.

关 键 词：脑明特铜矿床 锆石U-PB测年 地球化学 埃达克岩 蒙古-鄂霍茨克洋 

分 类 号：P618.41[天文地球—矿床学] P597[天文地球—地质学]